Extreme pressure grease



Patented Feb. 6, 1951 S PATENT OFFICE EXTREME PRESSURE GREASE John J.Kolfenbach, Somerville, and Rosemary OHalloran, Elizabeth, N. 1.,assignors to Standard Oil Development Company, a corporation of DelawareApplication July 1, 1949, Serial No. 102,584

6 Claims.

This invention relates to an improved extreme pressure lubricatinggrease composition and more particularly relates to an extreme pressuregrease composition which contains incorporated therein the alkalineearth metal salt of a high molecular weight sulfonate and in conjunctiontherewith alkaline earth metal salts of a low molecular weight alkylsulfonic acid and a low molecular weight carboxylic acid.

It has recently been found that the presence of the salts of lowmolecular weight carboxylic acids in combination with salts of highmolecular weight petroleum sulfonates imparts considerable extremepressure properties to the grease composition. This is apparently due tothe activation at high loads of the sulfur present in the sulfonate.This activation allows the formation of a metallic sulfide film which isevidenced by a black film appearing upon the wear area with which thegrease composition comes in contact.

It has now been found that a grease composition showing load carryingproperties superior to the grease compositions described above canbeprepared from sulfonates where a portion of the low molecular weightcarboxylic acid salt used is replaced by the salt of a low molecularweight alkyl sulfonic acid, in order to increase the amount of sulfurpresent in the formulation. Apparently it is necessary to retain some ofthe carboxylic acid salt in the product since, when all the lowmolecular weight carboxylic acid salt is replaced, the product is notoutstanding in extreme pressure properties. While the reason for thisphenomenon is not apparent, it is believed that the presence of the lowmolecular weight carboxylic acid salt aids in the activation of thesulfur present and. permits it to combine with the metal of the bearingsurfaces forming a protective metallic sulfide film.

It is the object of this invention, therefore, to provide an improvedextreme pressure lubricating grease composition which comprises admixingwith a mineral oilbase stock, a salt of a high molecular weight sulfonicacid, a. salt of a low molecular weight alkyl sulfonic acid, and a saltof a low molecular weight aliphatic carboxylic acid.

Experience has established in grease making and in the use of greasesthat it is'the best practice to select as the lubricating oil in thegrease, an oil of the same type as would have been selected if a liquidlubricant could have been used. A wide range of lubricating oils istherefore permissible in grease production. In general, the baseoilofthe compositions of the present invention comprises an oil having a S.S. U. in the range of from about 30 to 180 Saybolt Universal seconds at210 F. These lubricating oils may be either mineral lubricating oils orsynthetic lubrieating oils produced by methods familiar to the art.

The high molecular weight sulfonic acids which are employed in thegreases of this invention are suitably prepared by treating petroleumoils of the lubricating oil range with strong sulfuric acid. Thesulfonic acids are then converted to the desired salts, which in thepetroleum industry are well known by the name of petroleum sulfonates.The high molecular weight sulfonic acids which are employed havemolecular weights in the range from about 300 to about 600, preferablyfrom about 400 to about 500. The high molecular weight sulfonates canalso be derived from relatively pure sulfonic acids having from about 10to about 33 carbon atoms per mol. For example, sulfonated products ofalkylated aromatics such as benzene, toluene, xylene, etc., alkylatedwith olefins or olefin polymers of the type of polypropylene,polyisobutylene, etc., can be used. Likewise, alkyl sulfonic acids ofthe 300-600 molecular weight range are suitable. The high molecularweight sulfonates of the alkaline earth metals calcium, strontium andbarium are employed, the strontium sulfonates being especiallypreferred.

The low molecular weight alkyl sulfonic acids which are employed, forexample, methane sulfonic acid, ethane sulfonic acid, propane sulfonicacid, etc., have molecular weights in the range of 96 to 166,corresponding to C1 to C6 sulfonic acids.

' The salts employed are those of alkaline earth metals, of which thecalcium salt is preferred. 7

The low molecular weight carboxylic acid salt is preferably calciumacetate. However, in accordance with this invention, there may be usedany of the alkaline earth metal salts of low molecular weight carboxylicacids, such as formic, acetic, propionic, butyric, oxalic, furoic,lactic, etc.

The greases of the invention contain from about 10% to about 30% byweight of total salts The weight ratio of the high molecular weightsulfonate salt to the low molecular weight sulfonateplus carboxylic acidsalt may be from about 120.4 to about 1:1.25. The low molecular weightconstituents are employed in weight ratios of sulfonate to carboxylicsalt of from about 0.8 1 to about 7.5:1. For example, good greases canbe prepared which contain from 5 to 20 pref- Jeralily 10%, of highmolecular weight sulfonate,

2 to 6%, preferably 4%, of low molecular weight sulfonate, and 2.5 to7.5%, preferably 5%, of loW molecular weight carboxylic acid salt, thesepercentages being by weight and based on the weight of the totalcomposition.

EXAMPLE A series of greases was prepared containing of the strontiumsalt of petroleum sulfonic acid having a molecular weight of 450, andvarious quantities of calcium acetate and/or calcium ethane sulfonate.The following formulation is illustrative.

Composition 10% strontium sulfonate 5% calcium acetate, anhydrous 3.5%ethanesulfonic acid 1.5% hydrated lime 85.0% acid extracted coastalmineral oil, 55

S. U. S../210 F. viscosity Procedure The greases in the series werecomparable, all being prepared in the same mineral oil base stock .andusing the same general procedure. In preparing the greases containingcalcium ethane sulfonate, the free ethane sulfonic acid was dissolved intwice its weight of water and was neutralized with the hydrated lime.When the reaction appeared to be complete as evidenced by a drop in thetemperature to about 100 F., the neutralized solution was added to ablend of the strontium sulfonate and the mineral oil and the f batch wasstirred at 180 F. to 200 F. until no solid particles were present. Thenthe calcium :acetate was added as a 20% aqueous solution and the productdehydrated slowly, withstirring, .until a temperature of 300 F. wasreached. The product was cooled to room temperature without stirring,and was easily homogenized to a smooth grease structure.

The extreme pressure properties of the grease compositions of thisinvention containing mixed low molecular weight salts of sulfonic andcarboxylic acids were compared with greases containing either one or theother of these con stituents in an extreme pressure 4- ball testingmachine at various loads. In this test machine, one steel ball isrotated against three stationary balls at difierent loads, thusproducing Wear spots on the stationary balls. The .size of the wearspots is an indication of theanti-wear properties of the grease beingtested. In comparison with .a conventional extreme pressure grease, allof ,the sulfonate greases gave superior performance at high loads. Atvery high loads, however, the greases of the invention gave exceptionalperformances, as shown .by the .data in the following table:

TABLE-SULFONIATE GR'EXSES CONTAINING 10 WEIGHT P-ER CENTSTRONT-IUM SALTOF 450 MOL. WEIGHT PETROLEUM SULFONIO ACID 4-'Ball E. P. Testerwear SpotDiameter, m.-m. at 150 Load Low Mol. Weight Salts, Weight Grease Num-Per Cent 'bei' 5- Conventional :E. P-. Grease Welded The data in thetable show that whereas the conventional extreme pressure grease isincapable of supporting high loads, the greases which contained both lowmolecular weight sulfonate and low molecular weight carboxylic acid saltgave low wear spot diameters in the range 0.96 to 1.54 m. m. at the highload of kg.

The advantages of the greases prepared in accordance with the inventionare shown graphically in the accompanying Figure 1. In the figure wearspot diameter in millimeters from the 4-ball tester is plotted againstthe load in kilograms. It is to be noted that the grease compositions ofthe invention, exemplified by greases No. 1, 2, and 3, carry extremelyheavy loads in comparison with greases No. 4 and 5 which contain eitherlow molecular weight sulfonate or carboxylic acid salt. It is also to benoted that although greases No. 3 and No. 4 are substantially equivalentat about 125 kg. and at about kg, grease No. ,3 is superior within thisrange. Also shown in the figure are. the results obtained with theconventional extreme pressure grease comprising .sulfurized fatty .oilina lithium base grease, which was capable .of supporting only lightloads.

To summarize briefly, it has been found that an improved extremepressure grease composition may be made by incorporating into thedesired lubricating oil base stock, the desired amount of alkaline,earth metal salt of .a high molecular weight sulfonic acid that is .oilsoluble and water insoluble, .forexample, astrontium salt of a sulionicacid having a molecular weight within a range of .300 to 600 with analkaline earth metal salt of a low molecular weight sulionic acid thatis oil insoluble and Water soluble, for example, a calcium salt ofanalkyl sulfonic acid having a molecular weight within a range of from96 to 166, and an alkaline .earth metal salt of a low molecular Weight.carboxylic acid, for example, calcium acetate. It is to be understood,of course, that the percentages of the vari- .ous constituents may bevaried to produce the particular grease composition desired. It is alsoto be understood that various addition agents may be added to thesegrease com-positions to change their performance characteristics, forexample, oxidation inhibitors, viscosity index improvers, tack-messagents, and the like may be incorporated in the grease to modify thosecharacteristics.

What is claimed is:

1. ,An improved j'lubricating grease composition consisting essentiallyof a lubricating oil base stock having incorporated therein from about'5 to 20% of an alkaline earth metal sulfona-te prepared from asulfon-ic acid having a molecular weight within a range of from 300 to600, from about 2% to 6% by weight of an alkaline earth metal sulfonateprepared from alkyl sulfonic acid having a molecular weight within .arange of from 96 to 166 and about 2.5% to 7.5% of an alkaline earthmetal salt of an aliphatic carboxylic acid having from 1 to 4 carbonatoms.

2. :An improved lubricating r ase c p sition consisting essentially of alubricating oil base stock having incorporated therein about 5 to 20 byweight of an alkaline earth metal sulfonate prepared from a petroleumsulfonic acid having a molecular weight within the range of from 400 to500, from 2 to 6% by weight of an alkaline earth metal sulfonateprepared from an alkyl sulfonic acid having a molecular weight within arange of from '96 to 166, and from 7.5% t 2.5% by we ht or an alkalineearth metal salt-.0: an

aliphatic carboxylic acid having from 1 to 4 carbon atoms.

3. An improved lubricating grease composition consisting essentially ofa lubricating oil base stock having incorporated therein about by weightof a calcium sulfonate prepared from a sulfonic acid having a molecularweight of 450, about 4% by weight of a calcium alkyl sulfonate preparedfrom a sulfonic acid having a molecular weight of 110, and about 5% byWeight calcium acetate.

4. An improved extreme pressure lubricating grease composition whichconsists essentially of a lubricating oil base stock thickened to agrease consistency with a mixture of about 10% of waterinsoluble,oil-soluble alkaline earth metal salt of a petroleum sulfonate, about 4%of a watersoluble, oil-insoluble alkaline earth metal salt of an alkylsulfonate, and about 5% of an alkaline earth metal salt of an acidselected from the goup consisting of aliphatic carboxylic acids havingfrom 1 to 4 carbon atoms.

5. An improved extreme pressure lubricating grease composition whichconsists essentially of a lubricating 011 base stock thickened to agrease consistency with a mixt re of abo t 5 to 20% by weight of anoil-soluble, water-insoluble alkaline earth metal salt of a sulfonicacid, about 2 to 6% by weight of an oil-insoluble, water-soluble al- 6.An improved extreme pressure lubricating grease composition whichconsists essentially of a lubricating oil base stock thickened to agrease consistency with a mixture of about 10% by weight of a strontiumsalt of a sulfonic acid having a molecular weight of 450, about 4% byweight of a calcium salt of ethane sulfonic acid, and about 5% by weightof calcium acetate.

JOHN J. KOLFENBACH. ROSEMARY OI-IALLORAN.

REFERENCES CITED H'Ifhe following references are of record in the fileof this patent:

UNITED STATES PATENTS Name Date Zimmer et al July 13, 1948 Number

1. AN IMPROVED LUBRICATING GREASE COMPOSITION CONSISTING ESSENTIALLY OFA LUBRICATING OIL BASE STOCK HAVING INCORPORATED THEREIN FROM ABOUT 5 TO20% OF AN ALKALINE EARTH METAL SULFONATE PREPARED FROM A SULFONIC ACIDHAVING A MOLECULAR WEIGHT WITHIN A RANGE OF FROM 300 TO 600, FROM ABOUT2% TO 6% BY WEIGHT OF AN ALKALINE EARTH METAL SULFONATE PREPARED FROMALKYL SULFONIC ACID HAVING A MOLECULAR WEIGHT WITHIN A RANGE OF FROM 96TO 166 AND ABOUT 2.5% TO 7.5%